Method of soldering fabricated assemblies



J; ASKiN Dec. 30, 1941.

METHOD OF SOLDERING FABRICATED ASSEMBLIES Filed May 13, 1940 2 g d z 6L 2. i r g. /,/..////M//7 0 0 0 0 0 0 0 0 0 0 0 \0 0 0 0 0 0 X0 0 0 0 0 0 w \0 0 0 0 0 0 5 X0 0 0 0 0 0 0 0 c 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 p7 WV/X V// m M \NVENTOR Joseph/16km ATTORNEY Patented Dec. 30, 1941 METHOD OF SOLDG FAERICATED Joseph Askin, Buflalo, N. Y or to Fodder-s Manufacturing Company, lino, Bunnie, It, in.

Application May 13, 194G, Serial No. 33 M313 ((ll lit-412) 4 Claims.

This invention relates to a method and means ior soldering tine joints of the elements of cellular or laminated structures, such as radiators-oil coolers, and the like. i

In the practice. of the present process it is proposed to assemble the parts to be soldered in a irame or box, and to locate and to retain such parts in proper position through the aid of specially formed strips of solder alloy. The fusing of the solder is eflfected by the immersion of the entire assembly in a fused salt bath, and the simultaneous maintenance of mechanically applied pressure on the assembly during such immersion. This procedure insures the formation of proper joints, since the solder may be positioned between the joint surfaces directly, and as a result, when the solder-is melted it spreads and contacts joint areas which would otherwise be difilcult to reach.

The invention is more specifically set forth in the accompanying specification and drawing, wherein:

Fig. l is a side elevation of the soldering box;

Fig. 2 is an enlarged section on the line 22 of Fig. i; and

Fig. 3 is a top view or" the solder insert strips showing also a tube positioned upon the strips.

The invention is shown as organized to solder a radiator core it of the tube bundle type, whose components consist of a plurality of cylindrical tubes H having enlarged hexagonal heads l2. As is well known in the art, the tubes may be nested with the surfaces lZc of the heads I! in contact to form a typical cellular arrangement. tubes are formed of copper or brass, and they usually are of a thin walled section 0! about six-thousandths oi an inch.

The apparatus used in the soldering process consists of a holding fixture or box I i of alloy steel having bottom and side walls l5 and H3, respectively, which walls are proportioned to the size and shape of the radiator core to be assembled. The ends and the top of the box It are open.

The tubes are assembled directly in the box, wherein they are laid in successive horizontal rows, as shown in Fig. 2. It will be observed that narrow solder strips I8, which preferably are pre-iormed or corrugated (Fig. 3), are placed between the heads 52 of successive rows. Such strips perfectly match the shape of the heads it, so that the interposition thereof does not afiect use nesting of the tut-es. From a purely me= chemical viewpoint, it will be understood that the strips is at this point in the process serve as auxiliary fixtures, since they serve as guides to insure the proper spacing and alignment of the tube After the core is up to the desired height, a cover I I is placed on the upper row 01' tubes.

The

, strips iii are positioned directly between the til The cover it is slidably mounted between the side walls ii of the box, so that it is free to press down upon the underlying tubes. A weight or welghm to may be placed on the cover to increase the pressure on the tubes.

The box and assembled core therein are now immersed in a bath or molten salts and retained therein for a time suflci'ent to permit the fusing of the solder strips it. It is preferred that the tubes be retained in a horizontal position during this step, so that the salts may flow freely into the ends oi the tubes. Inasmuch as the solder joint faces of the core, it will be apparent. that, upon melting, the strips will rapidly disperse either by gravitational or capillary action between all at the contacting surfaces lie or the tube heads 82. r

During the melting oi? the insert strips 68, the rows of tubes will. tend to settle into closer coniormity, and this readjustment takes place auto matically, due to the pressure of the overlying cover E53 and accompanying weights iii. The cover thus serves as a pressure pad which socommodates itself to the rise and fall of the core mass, which movement may be caused by expansion and contraction of the tubes and/or the melting and subsequent setting of the solder when the box is removed from the salt bath.

Inasmuch as molten salt furnaces are. well known in the art, there isshown diagrammatically in Fig. 2 only the tank 25 thereof, with the salts level indicated by the numeral 26. It will be understood, therefore, that the temperature or" the bath is maintained within close limits atthe radiators or oil coolers for aeronautical installa-' tion, for example, silver solderiuais demanded,

in which melting temperatures are above 1000 F. In such cases, the strips is are formed oi the required solder alloy, which, to cite an example, may consist approximately of the following com-= patients:

lE-er cent sliver--- 50 Copper 16 Elite 16 Cadmium m... 18

It will be appreciated from the foregoing that the solder in itself may he costly than in radiator structures, and that the present process lends itseli to strict economy thereof, since the solder quantity may be accurately predeterminedby the thickness of the insert strips l8, and further, the advantageous positioning of the strips location at points only where it is required.

It has been found that the present process readily adapts itself to high temperature soldering of numerous other types of laminated or cellular assemblies. It will therefore be understood that, although the process is especially suitedto the type of structure herein described, the invention may be used on other structures or on other shapes or forms of radiators without departing from the inventive principle, as set forth in the following claims.

I claim:

1. The method of soldering cores formed of headed radiator tubes of the type described, which consists in assembling the tubes in a. box with strips of soldering material interposed between the heads of successive rows of tubes, placing the assembly under a predetermined and constant degree of compression by the application of a self-adjusting mechanical force to one side of the assembly lateral to said strips, fusing said solder strips while under such compression by immersing the assembly in a bath of molt n salt, and finally in removing the assembly from the bath to permit the cooling and setting of the solder.

2. The method of soldering cores formed of headed radiator tubes of the type described, which consists in assembling the tubes in nested relation with strips of soldering material interposed between the heads of successive rows of tubes, placing the assembly under a predeter- I mined and constant degree of compression by the application of a self-adjusting mechanical force to one side of the assembly lateral to said directly within the joints insures its ultimate strips, fusing such solder strips while under such compression by immersing the assembly in a bath of molten salt, and finally in removing the assem- -which consists in assembling the tubes in nested relation with strips of soldering material interposed between the heads of successive rows of tubes, placing the assembly undera predeteradequate to cause the fusing mined and constant degree of compression by the application of a gravitationalload to one side of the assembly lateral to saidstrips, fusing such solder strips while under such compression by immersing the assembly in a bath of molten salt 'with the tubes held in a horizontal position, and

finally in removing the assembly from the bath to permit the cooling and setting of the molten solder.

4. The method of integrating contacting end surfaces of an assembled bundle of tubes each of box, placing narrow strips of pre-formed solder material over the upper surfaces of the polygonal ends, superimposing a second layer of tubes and solder strips to form the tube bundle with the pre-formed strips interposed between the rows of tubes, whereby the pre-formed strips and the sides of the open-ended box serve as guides for positioning all of said tubes, and immersing the box and contained tubes and solder strips in a molten salt bath maintained at a temperature of the solder strips. JOSEPH ASKIN. 

